(SHOALS) - National Gypsum in Martin County has locked out their workers since Tuesday as part of an ongoing contract dispute between the company and its union worker.

National Gypsum Plant Manager said employees will return to work as soon as employees can vote on a contract and the contract is ratified.

United Steel Worker District 7 Jim Robinson released a prepared statement that said union members are standing up for the middle class. The company and the USW employees have not been able to agree on a retirement package.

Nancy Spurlock said the company and its workers at Shoals have been working without a contract since February 1.

Plant manager Greg Berry said he regrets the company had to lock workers out of the plant, but believes it is the next practical step towards reaching a contract agreement. He believes the company's offer that's on the table is fair and allows the company to remain competitive in the marketplace while continuing to provide jobs and benefits to it associated for the long term.

National gypsum is one of the largest producers of gypsum wallboard in the U.S. The Shoals plant and mine have been in production since 1956. It employs about 100 workers.